Articles | Volume 21, issue 5
Hydrol. Earth Syst. Sci., 21, 2449–2462, 2017
https://doi.org/10.5194/hess-21-2449-2017
Hydrol. Earth Syst. Sci., 21, 2449–2462, 2017
https://doi.org/10.5194/hess-21-2449-2017

Research article 10 May 2017

Research article | 10 May 2017

Ecohydrological optimality in the Northeast China Transect

Zhentao Cong1,2, Qinshu Li1,2, Kangle Mo1,2, Lexin Zhang1,2, and Hong Shen1,2 Zhentao Cong et al.
  • 1Department of Hydraulic Engineering, Tsinghua University, Beijing, 100084, China
  • 2State Key Laboratory of Hydroscience and Engineering, Beijing, 100084, China

Abstract. The Northeast China Transect (NECT) is one of the International Geosphere-Biosphere Program (IGBP) terrestrial transects, where there is a significant precipitation gradient from east to west, as well as a vegetation transition of forest–grassland–desert. It is remarkable to understand vegetation distribution and dynamics under climate change in this transect. We take canopy cover (M), derived from Normalized Difference Vegetation Index (NDVI), as an index to describe the properties of vegetation distribution and dynamics in the NECT. In Eagleson's ecohydrological optimality theory, the optimal canopy cover (M*) is determined by the trade-off between water supply depending on water balance and water demand depending on canopy transpiration. We apply Eagleson's ecohydrological optimality method in the NECT based on data from 2000 to 2013 to get M*, which is compared with M from NDVI to further discuss the sensitivity of M* to vegetation properties and climate factors. The result indicates that the average M* fits the actual M well (for forest, M*  =  0.822 while M  =  0.826; for grassland, M*  =  0.353 while M  =  0.352; the correlation coefficient between M and M* is 0.81). Results of water balance also match the field-measured data in the references. The sensitivity analyses show that M* decreases with the increase of leaf area index (LAI), stem fraction and temperature, while it increases with the increase of leaf angle and precipitation amount. Eagleson's ecohydrological optimality method offers a quantitative way to understand the impacts of climate change on canopy cover and provides guidelines for ecorestoration projects.

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Short summary
It is interesting to understand vegetation distribution and dynamics under water limitation in this transect. We apply Eagleson's ecohydrological optimality method in the NECT based on data from 2000 to 2013 to get M*, then compare with M from NDVI, furthermore to discuss the sensitivity of M* to vegetation properties and climate factors. The result indicates that the average M* fits the actual M well. The sensitivity analyses show how M* changes with vegetation characteristics and climates.